Zadok son of Ahitub and Ahimelech son of Abiathar were priests; Seraiah was the scribe;
David was not so engaged in his wars abroad as to neglect the administration of the government at home. I. His care extended itself to all the parts of his dominion: He reigned over all Israel (Sa2 8:15); not only he had a right to reign over all the tribes, but he did so; they were all safe under his protection, and shared in the fruits of his good government.
Commenting on 2 Samuel 8:15-18
And Zadok the son of Ahitub, and Ahimelech the son of Abiathar, were the priests,.... Not high priests, as Josephus (i) suggests, for there was only one high priest at a time; indeed there was a "sagan", or deputy priest, on occasion; and so Abarbinel says that Zadok was the high priest, and Ahimelech his second or deputy; but the truth of the case was...
Zadok . . . and Ahimelech . . . were the priests--On the massacre of the priests at Nob, [Sa1 22:19], Saul conferred the priesthood on Zadok, of the family of Eleazar (Ch1 6:50), while David acknowledged Ahimelech, of Ithamar's family, who fled to him. The two high priests exercised their office under the respective princes to whom they were attached.